I was re-watching some of the Animated episodes, and I noticed something about Sentinel Prime.
His chest isn't supposed to be the front of his vehicle mode. Sure, it kind of looks like it, but I think it is just supposed to sort of look like it while not actually being it.
I spotted this:

If you look at his back, you can see the front and the windshield of his vehicle mode on his back, just like the figure (except for some different colours)